This invention relates to a hydraulic linear actuator and, more particularly, the invention is concerned with providing an adjustable and lockable actuator suitable for use in confined areas for power actuation of a variable turbine nozzle and the like of a jet engine.
Modern high speed aircraft which reach speeds in the transonic range and beyond require that the variable nozzle of the turbine be adjustable and lockable over a wide range of configurations. This is generally accomplished by providing suitable actuators which include bellcranks and/or similar lever arrangements. Since it is extremely undesirable from the standpoint of increased aerodynamic drag to have any portion of the actuating mechanism protrude beyond the surface of the aircraft, the provision of an actuator which meets the requirement of being mechanically lockable at any position of its designated stroke within a small design envelope presents an extremely difficult problem. In addition, the actuator design must be capable of setting any desired stroke length at any position between the limits of the stroke. Electrical feedback is required to be proportional to the position of the load. Presently available actuators capable of satisfying the capabilities outlined require space that far exceeds that available in the nozzle portion of the turbine engine for mounting therein.